Process of treating sulfid ores.



NITED STATES PATENT Fries.

HUGH FITZALIS KIRKPATRICK-PICARD, OF LONDON, ENGLAND.

PROCESS OF TREATING SULFID ORES.

SPECIFICATION forming part of Letters Patent No. 665,744, dated January8, 1901.

Application filed June 28, 1900. Serial No. 21,988. (Specimens) To allwhom it may concern:

Be it known that I, HUGH FITZALIS KIRK- PATRIOK-PICARD, a subject of theQueen of England, residing at London, England, have invented a certainnew and useful Process of Treating Sulfid Ores, (for which I have madeapplication for Letters Patent under No. 2,151, dated February 2, 1900,)of which the following is a specification.

This invention has for its object the treatment of what are commonlyknown as complex sulfid ores-t. 6., those containing as chiefconstituents zinc, lead, gold, silver, and sulfur-of which type of oresthe Broken Hill sulfid ores are good examples.

The novelty of my invention consists in the manner in which these knownreactions are practically applied to smelting these complex ores,wherebycommercially successful results are obtained.

My process is briefly described as follows: The ore is first finelyground in any suitable mill and is then submitted to an oxidizing roastin a reverberatory furnace with the object of producing the maximumamount of oxids of lead and zinc and the minimum amount of sulfates. Thesulfurous gases produced during the roast may be collected and utilizedin any of the ordinary well-known ways. Inasmuch as it is impossible inordinary roasting practice to entirely convert all the lead sulfidpresent to lead oxid means must be taken to reduce to a minimum theamount of sulfate produced, and I find it useful after the first stageof roasting is finished, with the object of getting the oreas far aspossible in the form of oxids, to mix a small amount of coal-slack orother carbonaceous material with the roasted charge while still in thefurnace and to reheat the mixture for the further decomposition of suchsulfates. By these means a-high percentage of the lead sulfid isconverted into lead oxid, and for practical purposes the amount of leadsulfate left in the charge is of no importance. The amount ofcarbonaceous material added will vary according to the composition ofthe ore, butwill rarely exceed ten per cent. of the ore charge. Theroasted ore after removal from the furnace is mixed with coal or mixturewhich on carbonization will produce a coke and submitted to'azinc-distilling temperature in a retort or muffle-furnace in such a waythat the flames or gases from the furnace shall not come into directcontact with the ore charge. This operation may conveniently be carriedout in an ordinary zinc-distilling furnace. The result of this treatmentis the production of metallic zinc and metallic lead. At the ternperature of the furnace zinc is given off in the form of vapor, which iscondensed to metal in the usual way. The lead, gold, silver, iron, andsilica are left behind in the retort and suspended or hung up in acarbonaceous sponge or skeleton to be subsequently smelted.

In order to prevent the deleterious effect of the lead upon the retortsused, it is necessary to use an amount of coal of a bituminous characterin considerable excess of the amount theoretically required to reducethe oxids; but its actual amount will vary with the different ores undertreatment. The carbonaceous material cokes and forms a spongy matrix inwhich the particles of metallic lead, iron silicates, or other fusiblesubstances are retained, so that their harmful action upon the retort isprevented.

I find it greatly advantageous to briquet the charge of roasted ore andcarbonaceous material before charging the same into the furnace, withthe object of coking the mixtu re into coherent masses. For this purposebituminous coal or charcoal, anthracite, or similar material,inconjunction with a coking or binding material-such as tar, molasses,or pitch, or similarsuitable materialmay be employed. When briqueting isemployed, a less excess of carbonaceous material may be used.

By means of briqueting the reducing agent is more intimately broughtinto contact with the oxide than can be efiected by the best possiblemixture of the dry powders. Further, each briquet becomes an independentdistilling center, and the zinc vapor has no great distance to force itsway out, as it would in the case of mixed powders in bulk. Briquetingalso prevents the reduced lead particles from running together, and inconsequence of the metal being held in the form of minuteparticles-throughout the coke there is no danger of this metal attackingthe retort-walls, which otherwise, in the case of direct distillation ofthe powder, tends to happen with harmful results.

The residue after extracting the zinc by distillation, as hereinbeforedescribed, is smelted by any well-known method for the recovery of thelead and gold and silver and the separation therefrom of iron, silica,and other impurities that may be present.

Should any small amount of zinc be left in the residue, this will.largely be recovered with the subsequently-smelted lead and will serve auseful purpose in desilverizing the latter according to what is known asParkess method.

If the complex lead-zinc ore to be treated is considered too poor ineither constituent for practical smelting purposes, under this inventionit may be initially enriched to the required extent by the additionbefore grinding of galena or zinc-blende.

What I claim as my invention, and desire to secure by Letters Patent,is,

The process of treating sulfid ores containing silver, zinc and leadwhich consists in roasting the ore to the form of OXldS, mixing theroasted product with carbonaceous material suitable for coking, formingthe mixture into briquets, and distilling the briquets under suchconditions that they are first coked into coherent masses and finallythe zinc reduced and volatilized while the lead is reduced and the leadand silver retained in minute particles throughout the coke.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

HUGH FI'IZALIS KIRKPATRlGK-PIOARD.

Witnesses HAROLD WADE, HARRY DRIDGE.

